Differential Contact Pattern

[Fishfarmer]

Hi Guys, This is not about my 4500DT this time but same principal. I have a 1997 Mitsubishi Canter 6 tonne tipper and I have replaced the pinion and carrier bearings in the diff.

I needed to add a 2 thou shim on the pinion because the preload was too tight (these have a non crush sleeve type spacer). Before I put new bearings on the pinion I honed out the old ones so I could easily slip them on and off to try out different shim thicknesses. The spacer/shim is between the pinion head and bearing, so it difficult to take the new one off each time to try shims.

The original contact pattern was terrible, drive side near the toe and triangular or some of them dome shape (sunset as they say) I didn't have the correct size shim for under the pinion head so I cut one down to fit the shaft.
It was about 10 thou, about I/2 the original shim( 20 thou) under the pinion. This didn't seem to make much difference where the drive side contact pattern is.

I thought maybe just putting in the new bearings would get the pattern a lot closer to original ( original shim now put in).

These are pictures I have of my contact pattern. The coast side looks ok but I assume the drive side is too deep and close to the toe. I adjusted the backlash between the min/max specs at 8 thou to 12-14 thou.
there is a slight difference of the pattern coming in from the toe (two lots of drive pictures) but it is triangular and I am assuming is too deep in the tooth, and too near the toe. therefore from all the patterns I see on the internet I must, increase the pinion depth (lessen the shim thickness). Is there anyone who can help with an educated guess as to what shim size I should try. I dont want to keep taking this bearing on a number of times and off as its easy to damage.

Final comments, this pinion and ring gear still has meat on it, but it could be worn unevenly and giving me a bad tooth contact. Bearing preloads are correct on pinion and carrier, and backlash I adjusted a few times. Runout is just within spec of the manual at 4 thou. I put pressure on the ring gear as I turned the pinion.
Thanks, any advice will be helpful.

 

[Runs With Scissors]

A long, long time ago, I used to do Chrysler/Dodge/Jeep axles at as a dealer tech.

I was never particularly fond of using that patterning paste. It always seemed to be like "Black Magic/Voodoo" sort of thing to me.

In my opinion, there is no substitute for setting them up as close to the middle of the specs as you can get, by using the proper measuring tools.

Using the "factory tools" method, I almost never had a "comeback" (BTW those not familiar with the auto industry "comeback" is a 4 letter word....at least it used to be)

I will let others with more experience/authority comment on how to read that paste.

But if I was guessing, and I am......

I agree your coast side "looks" pretty good

I think your drive side is a little off and I would say to shim it near the bottom of the specs (i.e. thinner).


I have also heard that using different "brand names" of bearings to check the "set up" introduces more problems as the specs are slightly different. I can't speak to that, because I always used factory stuff, but its something to be aware of.

 

[Fishfarmer]

Thank you, appreciate your input. The pinion bearings are the same brand that came out (Koyo). Who knows who may have changed before I owned the truck. The carrier bearings are a different brand but the specs are supposed to be the same. Old bearings were NSK and the new ones are Koyo. But I run a contact pattern with the old NSK before I changed them, so I dont think the Koyos are the problem. Look forward to others you know may help. Thanks again, I always appreciate peoples time to give advice. P.S. I didnt run an original pattern prior to pulling it apart as carrier bolts had come loose. How I dont know, maybe someone didnt put red loctite on them. I had the truck for six years before that happened. Fortunately there didn't seem to be any damage to the teeth.

 

[BX25D Rookie]

I've done a lot of front/rear differential work on GM cars/trucks up to 1 ton full floaters in the past.
GM dealership service department environment for 25 + years.
Formerly, ASE Master Certified in all automotive categories and light trucks.
I am retired now and do all of my vehicles repairs and maintenance at home.
All, except for annual vehicle safety/emission inspections, and wheel alignments.

As long as you have reasonable preload on the carrier and pinion bearings, and some backlash,
it's pretty much "it is what it is" and doesn't really have any indication of proper function.
The "only" negative for such a differential setup is it "MAY" be noisy.
There are three driving conditions which may be noisy.
You might end up with one, two, all, or none.
1. Load - feeding the vehicle some throttle.
2. Float - steady accelerator pedal, maintaining a set speed on a flat road.
3. Coast - foot removed from accelerator pedal, using engine braking to gradually slow vehicle speed.

As you are aware, changing the shim on the pinion gear head (under the bearing, and the bearing is pressed in place) is difficult at best. Removing the bearing for changing the shim usually damages the bearing, and then replacing the bearing with another new bearing "theoretically" changes the setup pattern. So now you are in an unending situation where you cannot win.

So as long as you have reasonable pinion shaft bearing preload, and reasonable rotating torque for the pinion gear (with only the pinion gear and pinion bearings installed in the housing)
and reasonable carrier bearing preload, and some reasonable backlash, you will be good to go.

The wheels will go round and round and the vehicle will be usable.
Noisy? perhaps... However, 75W-140 gear lubricant will be your friend in that case

Many moons ago I owned and raced a rail dragster. Small block chevy and a powerglide.
During the original build and setup of the race car, I had a shifter malfunction.
It got shifted into reverse at racing speed driving down the 1/4 mile, and that was incredibly destructive.

It sheared the transmission input shaft (broke it) and the shaft stub was stuck in the torque converter.
It twisted the splines on both rear axles.
It broke off a differential ring gear tooth and damaged multiple pinion gear teeth.

I can weld, but that job required a professional. I know a guy.
He built up the broken ring gear tooth with TIG welding.
Also, repaired some chips in several pinion gear teeth.

Then multiple days with files, stones, and a Dremel and some Prussian blue.
That ring & pinion gear set was from a 1956 Oldsmobile Holiday 88, and was seriously obsolete.
Aftermarket gear sets were made from unobtanium, and completely unavailable.
And replacing the entire rear axle, housing and all, and narrowed, also was cost prohibitive.
I had purchased the rolling chassis used, and that was the rear axle in it when purchased.

Being a competition race car, gear noise was of no consequence.
I raced that car for many years with the welded up ring and pinion gear set teeth without any issues.

 

[Flintknapper]

I've done a lot of front/rear differential work on GM cars/trucks up to 1 ton full floaters in the past.
GM dealership service department environment for 25 + years.
Formerly, ASE Master Certified in all automotive categories and light trucks.
I am retired now and do all of my vehicles repairs and maintenance at home.
All, except for annual vehicle safety/emission inspections, and wheel alignments.

As long as you have reasonable preload on the carrier and pinion bearings, and some backlash,
it's pretty much "it is what it is" and doesn't really have any indication of proper function.
The "only" negative for such a differential setup is it "MAY" be noisy.
There are three driving conditions which may be noisy.
You might end up with one, two, all, or none.
1. Load - feeding the vehicle some throttle.
2. Float - steady accelerator pedal, maintaining a set speed on a flat road.
3. Coast - foot removed from accelerator pedal, using engine braking to gradually slow vehicle speed.

As you are aware, changing the shim on the pinion gear head (under the bearing, and the bearing is pressed in place) is difficult at best. Removing the bearing for changing the shim usually damages the bearing, and then replacing the bearing with another new bearing "theoretically" changes the setup pattern. So now you are in an unending situation where you cannot win.

So as long as you have reasonable pinion shaft bearing preload, and reasonable rotating torque for the pinion gear (with only the pinion gear and pinion bearings installed in the housing)
and reasonable carrier bearing preload, and some reasonable backlash, you will be good to go.

The wheels will go round and round and the vehicle will be usable.
Noisy? perhaps... However, 75W-140 gear lubricant will be your friend in that case

Many moons ago I owned and raced a rail dragster. Small block chevy and a powerglide.
During the original build and setup of the race car, I had a shifter malfunction.
It got shifted into reverse at racing speed driving down the 1/4 mile, and that was incredibly destructive.

It sheared the transmission input shaft (broke it) and the shaft stub was stuck in the torque converter.
It twisted the splines on both rear axles.
It broke off a differential ring gear tooth and damaged multiple pinion gear teeth.

I can weld, but that job required a professional. I know a guy.
He built up the broken ring gear tooth with TIG welding.
Also, repaired some chips in several pinion gear teeth.

Then multiple days with files, stones, and a Dremel and some Prussian blue.
That ring & pinion gear set was from a 1956 Oldsmobile Holiday 88, and was seriously obsolete.
Aftermarket gear sets were made from unobtanium, and completely unavailable.
And replacing the entire rear axle, housing and all, and narrowed, also was cost prohibitive.
I had purchased the rolling chassis used, and that was the rear axle in it when purchased.

Being a competition race car, gear noise was of no consequence.
I raced that car for many years with the welded up ring and pinion gear set teeth without any issues.

I would tend to agree with the above. It is essential to establish proper backlash and preload FIRST. That way you know you have acceptable pinion depth.

In some cases (especially with worn/used) gears it simply isn't possible to get that 'perfect' gear pattern. Personally, I want to see the drive side pattern as good as you can get it and not worry quite as much about the Coast Side.

OP states he has KOYO bearings to use (there is nothing better). So no worries there. From the patterns shown I'd like to see the drive side pattern come out of the toe a bit, but it isn't badly centered from the top land to the root.

You can see on this Dana 44 I set up... the drive side pattern is nicely centered and consistent in shape. The coast side much less so, but this gear set runs well and is not noisy.

I don't think the OP's set will achieve the same pattern, nor would it be necessary if not starting with a new gear set.

In short, you can 'chase' patterns until you are blue in the face. With used gears....I would pay more attention to proper backlash and preload.

 

[Lil Foot]

n short, you can 'chase' patterns until you are blue in the face. With used gears....I would pay more attention to proper backlash and preload.

A man after my own mind.